285/50R20 vs 285/55R20 at a glance
| Measure | 285/50R20 (current) | 285/55R20 (new) | Difference |
|---|---|---|---|
| Overall height | 31.22 in | 32.34 in | +1.12 in (+3.59%) |
| Width | 11.22 in (285 mm) | 11.22 in (285 mm) | +0 mm |
| Sidewall | 5.61 in | 6.17 in | +0.56 in |
| Wheel | 20 in | 20 in | +0 in |
| Circumference | 98.1 in | 101.6 in | +3.5 in |
| Revs per mile | 646.0 | 623.6 | −22.4 |
Verdict: check clearance and speedometer
Over 3% and up to 5%: worth checking clearance, the speedometer and gearing before you buy. Going from 285/50R20 to 285/55R20 is a 3.6% increase in overall height (+1.12 in), and the vehicle sits about 0.56 in higher. The tire is the same width. The 3% rule of thumb comes from Discount Tire and 1010tires; it is not a guarantee of fit.
True speed and odometer
| Speedometer shows | You are really doing | Difference |
|---|---|---|
| 35 mph | 36.3 mph | +1.3 mph |
| 45 mph | 46.6 mph | +1.6 mph |
| 55 mph | 57.0 mph | +2.0 mph |
| 60 mph | 62.2 mph | +2.2 mph |
| 65 mph | 67.3 mph | +2.3 mph |
| 70 mph | 72.5 mph | +2.5 mph |
| 75 mph | 77.7 mph | +2.7 mph |
Odometer: 1,000 indicated miles is 1,036 real miles, and 10,000 is 10,359.
The math
285/50R20: 20 + 2 × (285 × 50% ÷ 25.4) = 31.22 in. 285/55R20: 20 + 2 × (285 × 55% ÷ 25.4) = 32.34 in. Change = 32.34 ÷ 31.22 − 1 = +3.59%. True speed at 60 = 60 × 32.34 ÷ 31.22 = 62.16 mph.
Check next
- Regear and RPM at cruise for this swap
- Speedometer and odometer correction
- Other sizes within ±3% of 285/50R20
Calculated from the size alone. Real tires vary a little by brand and model, and the loaded radius is a bit smaller. Confirm the wheel width range, clearance, load index and speed rating for your vehicle. See how to read a tire size, the load index chart and the speed rating chart.
Size pages: 285/50R20 · 285/55R20. More swaps: all tire size comparisons.